Synthesis of pyrazole-based macrocycles leads to a highly selective inhibitor for MST3

Abstract

MST1, MST2, MST3, MST4, and YSK1 are conserved members of the mammalian sterile 20 kinase (MST) family. MSTs regulate key cellular functions such as cell proliferation, cell migration, metabolic regulation, and cell polarity. The MST3 isozyme plays a role in regulation of cell growth, autophagy and apoptosis, and its dysregulation has been linked to the occurrence of high-grade tumors with poor survival prognosis. To date, there are no isoform-selective inhibitors available that could be used for validating the role of MST3 in tumorigenesis and to assess its potential as an anti-cancer target for drug development. To this end, we have designed a new series of 3-aminopyrazole-based macrocycles based on the structure of an acyclic promiscuous kinase inhibitor. By varying moieties targeting the solvent-exposed region and optimizing the linker, macrocycle JA310 (21c) was synthesized. JA310 exhibited high cellular potency for MST3 with an EC50 = 106 nM and excellent kinome-wide selectivity with significantly lower cellular activity on the closely related kinase MST4 (EC50 = 1.4 uM). The high-resolution crystal structure of the MST3-JA310 complex provided intriguing insights into the distinct binding mode of the macrocycle, which was associated with large-scale structural rearrangements, including concerted induced-fit movements of the glycine-rich loop, the alphaC helix, and the activation loop. In summary, the developed macrocyclic MST3 inhibitor, JA310, demonstrates the utility of macrocyclization for the design of highly selective inhibitors and presents a first chemical probe for MST3.

Development of selective pyrido[2,3-d]pyrimidin-7(8H)-one-based Mammalian STE20-like (MST3/4) kinase inhibitors

“…However, we have recently developed a highly selective MST3 inhibitor using a macrocyclization strategy. 21 In the study presented here, we used a structure-based approach to shift the selectivity of the p21activated kinase 1 (PAK1) inhibitor G-5555 (8) towards kinases of the GCKIII subfamily, 22 eliminating the off-target activity for salt-inducible kinases 1-3 (SIK1-3) and other CAMK and STE family kinases. We studied the effects of the developed MST3/4-selective lead compounds on cell viability and cell-cycle progression and report their comprehensive characterization as chemogenomic compounds for these two interesting kinases.…”